When I first heard that the Union of Concerned Scientists was creating a research-based guide to green living, I was ecstatic. How brilliant, I thought, to finally have the answer to the question of which of the seemingly infinite "green" actions make the most difference. Should I obsess about turning the lights off before I left the house? Was composting worth the effort after all? UCS, which has a well-deserved reputation for accuracy and fact-based advocacy, seemed equipped to answer these conundrums once and for all.

Cooler Smarter: Practical Steps for Low-Carbon Livingcame out this week. And true to its promise, it uses research to determine which green actions make the most difference. I’m disappointed in the answers they came up with, though—not because they’re wrong or overly complicated, but because they’re not.

After two years of research, UCS found that the most important strategies for reducing a person’s carbon footprint are to change “what and how you drive, the energy you use at home, and what you eat.”

Those are answers we already knew. The vast majority of the green advice you’ll read? It’s irrelevant. There are four primary activities that dump carbon into the atmosphere: traveling from place to place, keeping buildings at pleasant temperatures, creating electricity, and raising animals for meat.

The rest of the green living pantheon—bamboo utensils, composting, eating local, reclaimed wood tables, organic cotton sheets—are nice gestures. And they often have other benefits: they might keep chemicals out of the water or provide a livelihood for local farmers. Many are also better than the alternatives they’re replacing. But when it comes to tackling climate change—not only the most dangerous environmental issue the world faces, but also a looming human rights problem—choosing these green products can only make a tiny difference.

If we already know how to live without creating so much carbon, that raises a more disturbing question: Why aren’t we doing it? There is any number of excuses: Fixing buildings requires investing a chunk of cash up front, and deciding on the right retrofits is a complicated process. Meat is too good to give up. Clean energy is more expensive. If Congress had only passed cap-and-trade, we wouldn’t need to be making these choices, because more carbon-intensive products would cost more and fewer people would buy them.

But we’re going to need to figure out how to make those choices. Researchers who study behavior change and climate have found that even if the world did agree to cap carbon emissions, people would still need to change their habits if the planet is to avoid the worst consequences a changing climate will bring. So now they’re experimenting with systems that can nudge people in the right direction. California is running a challenge, for instance, in which cities compete against each other to take smart green actions. At this point, we know the right steps to take. Now we just need to convince people to live more responsibly.